The present invention relates to an injection tube and in particular to such an injection tube which has at least one tube section provided with a continuously profiled contour and a central longitudinal channel extending through the tube section.
The invention also relates to a method of placing a ground anchor using an injection bore anchor of the above mentioned type, which includes the steps of producing a bore using a suitable flushing medium and introducing into the bore a self-hardening medium through a longitudinal channel on the injection bore anchor and the outlet bores of the longitudinal channel.
Injection bore anchors as such are known. They are structurally substantially equivalent to bore rods and/or injection tubes which, once the bore has been produced, can be used immediately as ground anchors and consequently remain as a lost tool within the bore hole.
An injection bore anchor is for example known from DE 37 24 165 C2. This known injection bore anchor comprises at least one anchor rod section which is provided with an outer thread over its entire length and a plate-shaped bore-crown which is provided with cutting edges and which radially overhangs the anchor rod section and is welded on to the end of the anchor rod section facing the bore hole bottom. A longitudinal channel which runs axially along the anchor rod section issues in the region of the bore-crown in an axial flushing bore, wherein transverse bores for flushing purposes are provided in a region directly adjacent to the bore-crown. Such an injection bore anchor is fundamentally suitable for producing bores and for the subsequent placing of ground anchors, wherein initially a bore is produced using a suitable flushing medium which emerges by way of the said flushing bore of the bore head and the said transfer bores. The flushing medium picks up the rocks which have been released as a result of the boring operation and flushes out the rocks in the direction of the bore hole outlet. Subsequently, the longitudinal channel is used in conjunction with the transverse bores for the purpose of introducing a self-hardening medium, e.g. a grout suspension, which enters in the region of the bore bead in the annular space between the outer side of the anchor rod section and the inner side of the bore hole and subsequently continuously fills the longitudinal channel from the bore hole bottom as far as the outlet of the longitudinal channel. During this filling operation, remaining cracks and crevices in the individual layers of rock are filled and in this way a reliable connection is produced between the ground anchor and the ground, this connection being further improved by means of the thread extending across the outer side of the anchor rod section.
Moreover, screw-on bore heads for bore rods and/or bore anchors are known from the brochure "Riploy, extension rod equipment", P & V (Mining & Engineering) Limited, Sheffield, England, 1971 as well as from DE 34 00 182 C2.
Ground anchors are used in tunnel construction and tunnelling for the purpose of stabilising cavity walls and in addition to this are also used to provide suspension safety devices. These ground anchors function substantially by producing a connection between the successive ground layers in the longitudinal direction of the anchor. The stabilising operation is particularly difficult in all cases where the layers to be connected to each other are regarded as having low cohesive properties, so that special measures are constantly necessary to produce a reliable anchorage.